Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$221.48	4.824%	$232.1642	$232.16	$232.15	$232.20
Purchase #2	$120.89	13.637%	$137.3758	$137.38	$137.40	$137.40
Purchase #3	$41.60	5.660%	$43.9546	$43.95	$43.95	$44.00
Purchase #4	$112.83	6.792%	$120.4934	$120.49	$120.50	$120.50
Purchase #5	$239.82	12.122%	$268.891	$268.89	$268.90	$268.90
Purchase #6	$249.28	9.647%	$273.328	$273.33	$273.35	$273.30
Purchase #7	$210.69	3.757%	$218.6056	$218.61	$218.60	$218.60
7 purchase totals =	$1,196.59		$1,294.8126	$1,294.81	$1,294.85	$1,294.90